How Cultivar and Extraction Conditions Affect Antioxidants Type and Extractability for Olive Leaves Valorization
Wafa Medfai, María del Mar Contreras, Antonio Lama‐Muñoz, Ridha Mhamdi, Imen Oueslati, Eulógio Castro
Abstract
Olive leafy biomass constitutes an attractive source of biological substances, such as oleuropein, which can be valuable for the production of functional extracts. The incorporation of this valorization in a biorefinery requires understanding how feedstock and extraction conditions affect the phenolic composition. Therefore, in this study, the phenolic composition of olive leaves from nine cultivars has been explored through using conventional maceration and ultrasound-assisted extraction (UAE). Two-way ANOVA suggested that both factors have a strong influence in the total extraction yield, total phenol content (TPC), and antioxidant activity of the extracts, but only the varietal type affected the solubilization levels. Pearson correlation showed different correlation trends between the TPC and the antioxidant activity depending on the extraction method. Hence, an in-depth analysis by liquid chromatography–mass spectrometry was performed. It showed that maceration and UAE provided the same solubilization of oleuropein. Nonetheless, the cultivar and extraction method affected the qualitative and quantitative phenolic composition of the extracts, including the content of oleuropein and some novel phenolic compounds. Furthermore, using principal component analysis, the extracts were clustered in four main groups, which could be useful for further standardization in potential biorefineries placed in Tunisia.